1. Field of the Invention
The present invention pertains generally to systems and methods for target tracking and beam steering. More particularly, the present invention pertains to systems and methods for automatic target tracking and beam steering wherein a series of video images obtained of a distant area containing a target are processed to automatically track the target, and the transmission path for a laser beam to be transmitted from a laser range finder is automatically steered or reconfigured so that the laser beam is steered to be aimed at the tracked target.
2. Brief Discussion of the Related Art
Laser range finders are available that transmit laser beams for being directed at a remote target in order to determine the distance or range to the remote target. Depending on the circumstances, the remote target may be located a considerable distance from the range finder. Laser range finders are conventionally designed to transmit the laser beam therefrom along a fixed transmission path. Laser range finders generally operate on the “time of flight” principle by measuring the time taken for the laser beam to travel to the target and be reflected back to the range finder. With the speed of the laser light being a known value, and with an accurate measurement of the time taken for the laser light to travel to the target and back to the range finder, the range finder is able to calculate the distance from the range finder to the target. Accurate range acquisition requires that the laser beam transmitted from the range finder be accurately focused, aimed or pointed at the intended target, which normally involves having the transmitted laser beam centered on the target as accurately as possible. Because the transmission path for the laser beam is fixed in conventional range finders, it must be manually aimed at the target by moving the range finder prior to actuating the range finder to transmit the laser beam for range acquisition.
One area in which laser range finders are useful is the area of weapons or firearms, where the range finders can be used to determine the distances to remote targets intended to be neutralized or destroyed using ammunition fired or discharged from the weapons or firearms. Acquiring an accurate range to the intended remote target is important to ensure that ammunition fired at the target will reach the target and/or will detonate at an optimal location for the target to receive the maximum effect from the ammunition. Modern technology has made it possible to produce infantry weapons including relatively small, hand-held firearms capable of delivering air bursting ammunition, such as air bursting grenades, shells and bullets, over considerable distances or ranges. Air bursting ammunition is of the type that is capable of detonating or exploding in the air, without requiring impact. Air bursting weapons will be equipped with sophisticated target acquisition/fire control systems that allow the weapon to be programmed so that the ammunition detonates at a detonation point located a particular distance from the weapon. In order for the weapon to be programmed with the detonation point needed to ensure that the maximum effect of the ammunition is delivered to a particular intended remote target, the operator or soldier must first acquire an accurate range to that target. A laser range finder integrated with the target acquisition/fire control system will allow the operator to acquire the range to the intended target for use in programming the detonation point. It is important that the acquired range be accurate, and that the range be acquired to the actual intended target and not to some non-targeted object or location, to ensure that the programmed detonation point is also accurate. The accuracy of the programmed detonation point is particularly important where the ammunition is primarily lethal in a lateral direction upon detonation. If the ammunition detonates too far in front of or behind the target, for example, the effects of the ammunition may miss the target and therefore the target may not be neutralized or destroyed. However, as explained further below, various circumstances and conditions can make accurate range acquisition difficult to accomplish. Accurate range acquisition may be especially difficult to accomplish under the conditions and time constraints imposed in military situations where weapons are used and in other similar situations.
Laser range finders are typically used in association with scopes or telescopic sights having an optical system with a visualization device, such as an eyepiece, at a viewing end of the scope allowing an operator of the range finder to directly view a magnified image of a distant area at which an aiming end of the scope is pointed. Weapons or firearms that have laser range finders are typically equipped with such scopes, and both the scope and the laser range finder may be mounted on or integrated with the body of the weapon or firearm thereby forming a structural unit. In the case of weapons that have target acquisition/fire control systems, this system too may be mounted on or integrated with the body of the weapon to be part of the structural unit. In order to find the range to an intended remote target, the operator must first position the aiming end of the scope to be pointed at the target, such that the target will be contained within the image seen by the operator through the visualization device, and the operator must then identify the target within the image seen through the visualization device. The optical system usually includes an aiming point such as a fixed ranging reticle superimposed over the image seen through the visualization device, and the operator must usually position the scope to center the reticle on the identified target as accurately as possible in order to accurately align the target with the transmission path of the laser beam to be transmitted from the laser range finder if actuated by the operator for range acquisition. Positioning the scope to center the reticle on the target ordinarily requires that the entire structural unit that the scope is part of be manually moved and positioned by the operator by hand. Because the scope's reticle is normally very small in size, the manual movement required of the operator to center the reticle on the target will usually need to be precise and well-controlled.
Difficulties may arise in range acquisition when the operator of the laser range finder must identify the intended target in the image observed through the visualization device. Oftentimes the target is not easily and/or quickly distinguishable by sight in the image seen by the operator through the visualization device. In many cases, for example, it may be very hard for the operator to visually detect, differentiate or discriminate the target from the background and/or from other objects or features contained in the image seen through the visualization device. In military situations, potential targets are in fact routinely camouflaged or otherwise deliberately made to look similar to their surroundings. Furthermore, despite magnification, the target may appear quite small in the image seen through the visualization device due to the target being a considerable distance from the operator. Consequently, the operator may require more time to study the image and/or may make an error in target identification. Making an error in target identification may result in acquisition of a range to an object or location that is not the correct intended target. If this range is relied on to program the detonation point for ammunition fired from a weapon, the ammunition will not detonate at the optimal location for the correct intended target to be neutralized or destroyed and in fact may cause unintended damage.
Range acquisition may also be more difficult where there is extraneous movement of the operator and/or movement of the intended target. In particular, manually moving and positioning the scope, and/or the entire structural unit that the scope is part of, by hand in order to center the scope's reticle on the target is made considerably more difficult when the operator experiences unintentional extraneous movement and/or when the target is a moving target. Unintentional extraneous movement of the operator of a laser range finder may be caused by various conditions intrinsic or extrinsic to the operator that result in unintentional movement being imparted to the hand or hands of the operator. Operators, such as soldiers in an active military situation, facing stressful conditions and/or constantly varying or unpredictable environmental conditions are especially prone to experience unintentional extraneous movement that interferes with the operator's ability to align an intended target with the transmission path of the laser beam to be transmitted from the range finder. Unintentional extraneous movement of an operator may be caused, for example, by operator jitter or unsteadiness, by physical or emotional stress, by respiration, by heartbeats, by vibration or other movement of a vehicle, surface or structure in or on which the operator is located, and/or by various other conditions. Unintentional extraneous movement of the operator impairs the operator's ability to execute controlled manual movement of the scope and/or other associated structure so that the scope's reticle, and therefore the transmission path of the laser beam to be transmitted from the range finder, are accurately aimed at the target and makes it very difficult for the operator to hold the scope and/or other associated structure steady in a position where the reticle, and therefore the transmission path of the laser beam, are accurately aimed at the target long enough to perform range acquisition. Even in the case of a stationary target, the problems arising from unintentional extraneous movement of the operator increase the time it takes to obtain an accurate range due to the inherent difficulties associated with manually aiming the reticle, and therefore the transmission path of the laser beam, at the target and keeping the reticle and the transmission path of the laser beam aimed at the target long enough to acquire the range to the target.
Accurately aligning the target with the transmission path of the laser beam to be transmitted from the range finder may also be more difficult when the target is in motion due to various conditions intrinsic or extrinsic to the target, and especially when the target is attempting to evade detection. When the target is in motion, the operator will ordinarily need to manually move the scope and/or other associated structure to follow the moving target with the scope's reticle. Similar to the situation where the operator experiences movement, the moving target situation increases the difficulty of range acquisition and increases the time it takes for the operator to obtain an accurate range. The problems associated with following a moving target are exacerbated when the operator experiences unintentional extraneous movement while at the same time attempting to follow the moving target.
Where the scope is associated with structure, such as a heavy weapon, forming a heavy structural unit that must be manually moved and positioned in conjunction with aiming the transmission path of the laser beam at the target, the mass of the structural unit or associated structure may make it more difficult for the operator to execute the controlled manual movement needed to follow the target, to accurately aim the transmission path of the laser beam at the target, and to maintain the transmission path of the laser beam aimed at the target long enough to acquire the range to the target. The small size of the reticle may further increase the demand on the operator for controlled, precise manual movement of the scope and/or associated structure. The increased difficulty or demand on the operator arising from the mass of the structure that needs to be moved and/or the small size of the reticle are exacerbated when the target is in motion and/or when the operator experiences unintentional extraneous movement as described above.
Accordingly, it can be an extremely challenging task for an operator of a laser range finder to correctly identify an intended target and obtain an accurate range or distance measurement to the intended target, particularly in the event of movement of the target and/or unintentional extraneous movement of the operator, and particularly under the conditions in which laser range finders are often used.
Weapons, such as guns, that are equipped with conventional laser range finders must normally have the range finder “calibrated” to the weapon. Usually the weapon has a barrel or bore from which ammunition is discharged when the weapon is triggered or fired. In order for the laser range finder to acquire a range to the target that accurately correlates with the optimal distance from the end of the barrel for the ammunition to reach the target and/or at which the ammunition must detonate to deliver its maximum effect to the target, it is important that the transmission path of the laser beam that would be transmitted from the range finder for range acquisition be exactly parallel (within achievable limits) to the barrel of the weapon. Consequently, it is currently necessary to “calibrate” laser range finders to their associated weapons by mechanically adjusting the position of the range finder relative to the weapon as needed for the fixed transmission path of the laser beam to be parallel to the barrel of the weapon. The mechanical calibration process has numerous disadvantages including being tedious, being time consuming, and being subject to human error.
U.S. Pat. No. 6,145,784 to Livingston is representative of a target tracker implemented in conjunction with a laser weapon for tracking targets, namely missiles in flight. In one embodiment, the target tracker illuminates the target with radiation of a first wavelength and a laser beam from the laser weapon engages the target and forms a hit spot thereon. An optics subsystem receives and detects both the illuminated target and the hit spot, and the laser beam is steered by a controller in response to the detected target and hit spot locations. In another embodiment which does not include an illuminator laser, an optics subsystem of the target tracker separately images the target radiation and the laser hit spot radiation through use of a blocking filter. The blocking filter ensures that only radiation at the target radiation wavelength passes to a first detector, while only radiation at the target hit spot wavelength passes to a second detector. A controller then steers the laser beam generated by the laser weapon in response to the detected target and target hit spot locations. In addition to being mechanically and procedurally complicated, the systems contemplated by Livingston are not covert and are not small enough in size to be practically implemented in a manner to assist an operator or soldier operating a hand-held weapon or device. Rather, the fact that the systems are designed for in-flight missiles requires that they be heavy and large in size.
U.S. Pat. No. 7,022,971 B2 to Ura et al is illustrative of a laser measurement apparatus employing laser beams to perform measurements capable of tracking a targeted moving object in a pre-defined environment. Laser beams of different wavelengths are required to be directed toward a corner cube attached to the object, thereby requiring that the object be “cooperative”. Steering of a laser beam is implemented via a complicated arrangement involving a motor for rotating a reflecting mirror and a motor for rotating a case that houses the reflecting mirror as well as the other major components of the apparatus. The steering arrangement disclosed by Ura et al is not one that could be practically miniaturized for use in a hand-held device.
U.S. Pat. No. 6,031,606 to Bayer et al presents another example of target tracking involving a cooperative or voluntary target. The target is detected automatically and its angular coordinates are determined automatically in accordance with two-dimensional image coordinates obtained by processing a pixel image of the target. The target tracking is designed for geodesic measurements, and the device disclosed by Bayer et al for accomplishing target tracking is a theodolite.
A weapon aiming system incorporated in manually aimed weapons, particularly machine guns, is represented by U.S. Pat. No. 5,686,690 to Lougheed et al. The aiming system uses a sensor for providing a video signal or series of frames representing a field of view, a video display device for displaying the field of view, and a digital signal processor for processing the video signal. The weapon may optionally include a separate laser range finder for measuring the range to a target and supplying the measurement to the signal processor. The system is designed to allow an operator to operate the weapon via the video display, which provides the field of view of the weapon as well as additional information such as boundary masks and a ballistic-corrected aim point, i.e. the point where the weapon would hit if fired, taking into account the range to the target.
U.S. Pat. No. 6,973,865 B1 to Duselis et al pertains to a system for evaluating the performance of a weapon system and of a human gunner operating an automated fire control system. The evaluating system is designed primarily for training purposes. The main concept of the system involves co-aligning a camera with the barrel of a weapon and imaging the target, or at least the direction toward which the barrel is aimed, at the time the weapon is fired. The evaluating system includes a firing-image source having a known imaging relation relative to a pointing direction of the barrel of the weapon. The firing-image source produces a firing image upon receipt of an image trigger command from the fire control system, which requires an electronic trigger. A computer receives the firing image and determines a calculated strike location from the firing image and from the range of the gun to a target.
A method and apparatus for processing images acquired via an electro-optical system is disclosed in U.S. Patent Application Publication No. US2006/0188169 A1 to Tener et al. The method and apparatus pertain primarily to image enhancement and rely on multiple images of the same object being captured by the electro-optical system. More specifically, the quality of the overall image is improved through registration, averaging, filtering, and other image processing techniques.
In view of the difficulties associated with target tracking, as defined herein to include identifying or detecting a remote target as well as following its position, it would be advantageous to provide a system and method for automatic target tracking that facilitate and assist in identifying and following an intended remote target by capturing and processing a series of video images containing the remote target. In view of the problems associated with aiming the transmission path of a laser beam to be transmitted from a laser range finder at a remote target, it would also be advantageous to provide a system and method for beam steering by which the transmission path for a laser beam to be transmitted from a laser range finder is automatically steered to be accurately aimed at the target that is tracked by the target tracking system. Providing systems and methods for automatic target tracking and beam steering would decrease the time required to correctly identify intended targets and obtain accurate range measurements to the correct intended targets, would ease the difficulties facing operators of laser range finders, would automatically compensate for movement of the target and/or extraneous movement of the operator, and would be useful for various purposes and/or in various practical applications in addition to range finding. Furthermore, it would be advantageous to provide automated systems and methods for target tracking and beam steering that are capable of being embodied in a structural assembly that is miniaturized or made small enough in size for it to be integrated into a hand-held weapon system or other hand-held portable device, and especially for it to be integrated into a target acquisition/fire control system of a weapon system. Providing automated systems and methods for target tracking and beam steering having the aforementioned features would expand the types of practical applications and the types of devices in which automatic target tracking, automatic beam steering, and/or automated-assisted range finding can be effectively and advantageously implemented. An additional area of use in which automatic target tracking and beam steering systems and methods would be advantageous involves calibration, and especially calibration of laser range finders, where the transmission path of a beam must be accurately positioned with respect to a feature of reference, such as the barrel of a weapon. Automatic target tracking and beam steering systems and methods that can be used for calibrating laser range finders to weapons would allow calibration to be performed electronically, thereby obviating the need for mechanical calibration and its attendant drawbacks.